Drawing instrument

ABSTRACT

A drawing compass-like instrument for producing spiral-like curves in which a worm is positioned on one leg of the instrument and a worm gear is positioned on the other leg of the instrument, the worm gear meshing with the worm. The worm is prevented from turning as the instrument is swung, whereby the gear swings around the major axis of the worm, causing the gear and the leg to which it is attached to increase or decrease the radius of the instrument as a function of the angle through which the instrument is swung.

United States Patent 1 1191 McDow 1111 3,797,119 [451 Mar. 119, 1974 DRAWING INSTRUMENT [76] Inventor: Ronald McDow, 10100 La Placita Dr., Rancho Cordova, Calif. 95670 [22] Filed: May 24, 1973 [21] Appl. No.: 363,585

[52] US. Cl. 33/27 M, 33/27 R, 33/27 B, 33/149 R, 33/153 G [.51] Int. Cl. B43] 13/24, GOlb, 3/16 [58] Field of Search 33/27 B, 27 R, 27 M, 149, 33/153 [56] References Cited UNITED STATES PATENTS 138,053 4/1873, Stebbins 33/27l 85.5,1-20 5/1907 Muhlbach. 33/27 M 1,292,086 l/l9l9 Schenck 33/27 B FOREIGN PATENTS OR APPLICATIONS 8,840 10/1905 England 33/27' M 17,536v 11/1958 Germany ..33/27 Primary Examiner-Willaim T. Dixson, Jr. Assistant Examiner-Bruce l-l. Bernstein Attorney, Agent, or Firm-Ernest L. Brown [5 7 ABSTRACT A drawing compass-like instrument for producing spiral-like curves in which a worm is positioned on one leg of the instrument and a worm gear is positioned on the other leg of the instrument, the worm gear meshing with the worm. The worm is prevented from turning as the instrument is swung, whereby the gear swings around the major axis of the worm, causing the gear and the leg to which it is attached to increase or decrease the radius of the instrument as a function of the angle through which the instrument is swung.

14 Claims, 11 Drawing Figures DRAWING INSTRUMENT BACKGROUND OF THE INVENTION Various instrumentshave been designed for producing spirals or scrolls. One of the earliest is shown in U.S. Pat. No. 138,053 which issued Apr. 22, 1873 to E. E. Stebbins for an Instrument for Drawing Scrolls. The apparatus was a compass-like instrument in which the base leg carried a lead screw. A lead screw follower was turned about the lead screw by an arm which was connected to the drawing arm of the compass. As the instrument was swung, the radius of the drawing .arm gradually increased or decreased.

U.S. Pat. No. 2,607,118 issued Aug. 19, 1952, to V. Debs for a Combination Compass and Ellipsograph. The compass had two arms which were spring biased outward. As the compass was swung, a string wrapped into grooves on one leg of the compass, the end of the string being connected to the other leg of the compass, thereby shortening the radius and causing the compass to produce a spiral curve.

U.S. Pat. No. 1,002,749 pertains to a beam compass wherein the beam rider is caused to have a varying radius relative to a fixed point by attaching thereto a serrated wheel which produces a radial component of force as the compassis swung. As the compass is swung, the serrated wheel moves in a spiral, forcing the 7 drawing instrument to which it is attached to ride farther out or farther in toward the center post along the beam of the beam compass.

Other spiral scribers are shown in U.S. Pat. No. 855,120, which issued May 28, 1907 to M. C. Muhlbach and U.S. Pat. No. 157,841, which issued Dec. 15, 1874 to H. King for a Scriber.

BRIEF DESCRIPTION OF THE INVENTION The apparatus contemplated by this invention may be described as a modified drawing compass. One of the legs, which in the compass would be the center leg but is called herein the base leg, has a plurality of pins on the foot thereof to prevent its turning. A removable mechanical worm is positioned near the top'of the base leg and has a shank which fits into the sleeve of the base leg substantially along the axis thereof and is firmly attached to the foot of the base leg so that it does not turn. The other leg of the drawing instrument, herein called the drawing leg, has a segmented worm gear upon a spindle or pivot and is typically splined to the drawing leg to cause the drawing leg'to turn with the gear. The segmented worm gear meshes with the mechanical worm so that as the instrument is swung, the worm gear is swung around the worm, whereby the worm gear and its attached drawing leg assumes a continuously changing radius relative to the base leg to produce a spiral-like curve. Typically the radius increases or decreases substantially linearly as a function of the angle through which the instrument is turned. The worm may be either a clockwise or a counterclockwise worm, whereby swinging the instrument in a particular direction may selectively increase or decrease the radius of the instrument.

In a preferred embodiment, the worms and worm gears form matched sets, and the pitch of the worm and gear may be chosen to produce various spirals. The sets of worms and worm gears are preferably interchangeable, and keepers are provided to hold a worm and a worm gear onto the drawing instrument during its use.

It is therefore an object of this invention to provide a means for producing spiral-like curves.

It is another object of this invention to provide a drawing compass-like instrument having a variable radius whose radius is positively controlled by a worm and worm gear combination, the radius of the compass being a linear or non-linear function of the angle through which the instrument is swung.

. BRIEF DESCRIPTION OF THE DRAWINGS Other objects will become apparent from the following description, taken in connection with the accompanying drawings.

FIG. 1 is a side view of a typical apparatus of this invention.

FIG. 2 is a view, partly in section, taken at 2-2 in FIG. 1.

FIG. 3 is a view taken at 3-3 in FIG. 1.

FIG. 4 is a view taken at 4-4 in FIG. 1.

FIG. 5 is a view taken at 4-4 in FIG. 1 with the worm and worm gear removed and the worm keeper and worm gear keeper in their open position.

FIG. 6 is a sectional view of the set screw engaging the worm keeper.

FIG. 7 is a view of the back of FIG. 1.

FIG. 8 is a view of the worm shank or shaft and its surrounding sleeve.

FIG. 9 is a fragmented sectional view, taken from the bottom in FIG. 4, showing the worm gear keeper of this invention.

FIG. 10 is a view taken at 10-10 in FIG. 9.

FIG. 11 is a view taken from the right in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION The apparatus of this invention may be described as a modified drawing compass. One of the legs 20, which in the compass would be the center leg but is called herein the base leg, has a plurality of pins 22-30 (shown more particularly in FIG. 3) on the foot 32 thereof to engage the paper and to prevent turning and translation of the base leg 20. The main body 34 forms a sleeve to receive the shank or shaft 36 of a mechanical worm 38. The shaft 36 has detent 40 for engaging a set screw 42 through the thrust bearing collar 41 which prevents relative turning between the shaft or shank 36 and the collar 41 about an axis defined substantially along the axis of the shank 36. Typically a second set screw 33 attaches the base to the shaft 36.

The worm 38 fits over the shank 36 and is prevented by the flat 44 from turning.

1 Alternative embodiments could make the worm 38 and the shaft 36 in one piece.

Still other alternative embodiments could make the collar 41 integral with the shaft 36.

The worm 38 has any desirable pitch depending upon the desired functional relation between the increase in radius of the instrument and the angle through which the instrument is swung. Further, the worm 38 may be pitched in one direction or the other, depending upon whether it is desired to increase or decrease the radius of the instrument when the instrument is swung in a particular direction.

The worm 38 is replaceable, and it may be replaced by other worms with different pitches and directions of slope. A keeper 46 is provided to hold the worm onto the instrument during use, and the keeper 46 may be moved aside, as shown in FIG. 5, to allow the worm to be removed and replaced. The keeper 46 isa plate which is pivoted by a pivot 47 at one corner relative to a frame 50 about an axis substantially parallel to the axis of the worm 38. The plate covers most of the end of the worm 38, as shown in FIG. 4, with the end of the shaft or shank 36 fitting into a recess 48 which is loose enough to allow swinging of the instrument. The keeper 46 is held in its closed position by a set screw 52 which is shown more particularly in FIG. 7. The set screw engages a detent 54 in the keeper plate 46, as shown more particularly in FIG. 6.

To remove the worm 38 and replace it with another worm, the set screw 52 is loosened to disengage the detent 54. The keeper 46 is then swung from the postion shown in FIG. 4 into the position shown in FIG. 5. The worm 38 may then be slid off of the end of the shaft or shank 36. If the worm and shank 36 were integral, the entire assembly may be removed by loosening the set screws 33 and 42 as well as moving the keeper 46 out of the way.

The frame 50 is rigidly attached to the sleeve 34 as by the screws 51, 53 shown in FIG. 7, and its supports a pin or shaft 56 whose axis is normal to the axis of the worm 38 and to which a drawing leg 58 is rotatably attached. The upper end of the drawing leg 58 has a clevis formed by the members 66 and 68 which straddles the frame 50 and is rotatably connected to the pin 56. A clearance space 70 between the clevis members 66 and 68 allows the drawing arm 58 to rotate while still clearing the frame 50. A spline or key 60 is rigidly attached to the upper portion of the leg 58, and is directed generally in a radial direction relative to the axis of the pin 56. A segmented worm gear 62 carries a slot 64 on one side thereof of size to slidingly engage the key or spline 60. The worm gear 62 carries teeth on the periphery thereof which match the teeth of the worm 38. The pitch of the worm 38 and the pitch of the gear 62 are substantially matched.

The gear 62 has a hole formed in the center thereof to allow it to be slipped over the end of the shaft 56. Preferably the gears 62 are interchangeable so that the worm 38 and gear 62 may be interchanged in sets. To put the gear 62 onto the leg 58, one opens the keeper 72 and slides the gear 62 onto the shaft 56 and over the spline 60. The keeper 72 is then closed, locking the gear 62 into substantially rigid engagement with the leg 58.

A slot 74 in the end of shaft 56 accommodates the cam 76 of the keeper 72. The cam 76 is of small enough width that when the end of the cam projects substantially coaxially with the axis of the shaft 56, as shown in FIG. 5, the gear 62 may he slipped over both the shaft 56 and the keeper cam 76. The cam 76 is supported for turning about the axis of a pin 78 which is positioned diametrically across a diameter of the shaft 56 through the slot 74 as shown particularly in FIGS.

A spring 80 is positioned substantially coaxially into a countersunk hole in the end of shaft 56. The cam 76 has a detent 82 which, when the cam 76 is moved into its closed position shown more particularly in FIGS. 4 and 9 engages the spring 80 and is held in position until the cam 76is forcefully dislodged and moved into its open position.

The leg 58 may be in one continuous length, or it may be made in two or more pieces as shown by the length 84 which is hinged relative to the upper portion of the leg 58 at the hinge 86 and is held in position by a set screw in accordance with the known principles of drawing compasses. Extensions may be added, if desired, to the leg 58, and the leg 58 may be splined or telescoped (not shown) to have an adjustable length. Such splining or telescoping is known in the art of drawing compasses, and for convenience need not be shown here. The bottom end of the drawing arm 58 has a chuck for receiving a drawing instrument such as a pencil 88 or a drawing pen (not shown). The chuck, typically, is closed by means of a chuck screw 90.

In operation, to draw a spiral upon a piece of paper, the desired worm 38 and worm gear 62 combination is selected and placed into the instrument as described above. The base leg 20 and worm 38 is then turned relative to the worm gear 62 to adjust the initial radius of the instrument. Alternatively, the base leg 20 may be held stationary while the gear 62 is turned about the base leg 20 and the worm 38. Still another way of setting the initial radius is to open the keeper 72, slipping the gear 62 off of the shaft 56, adjusting the radius, and placing the gear 62 back onto the shaft 56 then relocking the keeper 72 into the position shown in FIG. 4.

With the proper selected worm 38 and gear 62, and with the selected initial radius of the spiral, the base leg 20 is then placed onto the paper with the center pin 26 positioned at the center of the spiral. One may then take hold of the frame and turn it, together with the drawing leg 58, gear 62 and keeper 46 about the axis of the shaft 36 and worm 38. As the instrument is swung in this fashion, the gear 62 rotates about the worm 38, causing the radius of the drawing arm 58 to increase or decrease depending upon the direction of tilt and the pitch of the worm 38 and the teeth of the gear 62.

Thus, the instrument of this invention is a novel and useful drawing instrument for drawing spirals in which the worm 38 and gear 62 may readily be removed and replaced by another worm and gear set having a different pitch and a different direction of inclination to cause the spiral to spiral either inward or outward as the instrument, for example, is rotated clockwise, and to allow the spiral to increase rapidly or slowly depending upon the pitch of the worm 38 and the gear 62.

If desired, the instruments may be fabricated of plastics material, as low cost instruments, with or without keepers for the worm 38 and gear 62.

Although the invention has been described in detail above, it is not intended that the invention should be limited by that description, but only by that description when taken in combination with the words of the appended claims.

I claim:

1. A compass-like drawing instrument for making spiral-like curves comprising:

a base leg, having a major axis defined along the length thereof, including means thereon for fixedly engaging a reference position on a drawing to prevent translation of said base leg relative to said referenced position and to prevent rotation of said base leg about said major axis;

a drawing leg, rotatable about said base leg and pivoted about a pivotal axis to vary the radius of the instrument relative to said base leg and said reference position and adapted to hold a drawing tool on the end thereof distal from said pivotal axis; a mechanical worm, positioned on said base leg with its axis substantially parallel with the said major axis of said base leg, including means for prevent- I ing said worm from turning about said axis; and

a worm gear, rigidly attached to said drawing leg for rotation about said pivotal axis and meshing with said worm.

2. A drawing instrument as'recited in claim 1 in which said worm and worm gear are each removable from said legs.

3. Apparatus as recited in claim 2 and further comprising keepers for holding said worm and said worm gear onto their respective legs.

4. Apparatus as recited in claim 3 in which said worm and worm gear form a matched set, said set being interchangeable with other matched sets to vary the functional relation between the spread angle of the legs of the instrument and the angle through which the instrument is swung.

5. In combination:

a drawing compass having two legs pivoted about a pivotal axis, one of which supports a worm whose axis along the length of its supporting leg and which is attached for non-rotation about said second axis;

and

a worm gear, fixedly attached to the other said leg for rotation about said pivotal axis of said compass and meshing with said worm to cause the radius of said compass to vary as said compass is swung.

6. Apparatus as recited in claim 5 in which said worm and worm gear form a matching set, and said set is interchangeable with other matching sets having different pitches and directions of spiral of said worm and gear.

7. Apparatus as recited in claim 6 and further comprising a first keeper for holding said worm onto said compass and a second keeper for holding said gear onto said compass.

8. An instrument as recited in claim 7 and further comprising a plurality of paper-engaging pins upon the foot of said leg which supports said worm.

9. Apparatus as recited in claim 8 and further comprising a marking implement attached to the foot of said gear-carrying leg.

10. A compass as recited in claim 9 in which said gear-carrying leg has a hinge therein and including a set screw for fixing a position of said hinge.

11. A drawing instrument of the compass type for producing spiral-like curves comprising:

a first leg including a rotatable sleeve and having a plurality of projecting spikes from the foot of said leg; a mechanical worm having a shank thereon shaped to fit into said sleeve along an axis defined in said first leg including attaching means positioned and adapted to attach said shank and said foot to allow turning of said sleeve relative to said shank about said axis;

a frame, attached to said sleeve for rotation about the axis of said worm;

a second leg pivotally attached to said first leg for rotation about a second axis, relative to said frame, substantially perpendicular to the axis of said worm and said shank;

a spline on said second leg;

a segmented worm gear having a groove adapted to mate with said spline in the non-tooth portion of said gear to prevent relative rotation between said gear and said second leg;

a shaft on said second leg substantially coaxial with said second axis;

' said gear being positioned on said shaft and said spline to cause said second leg to turn with said gear;

a first keeper on the end of said shaft, positioned and adapted to hold said gear on said shaft, including a spring detent for holding said keeper in its gearholding position;

a second keeper having a blocking plate, pivotally attached to said frame to have at least two positions, one of which prevents the removal of said worm and the other of which allows removal of said worm and including means for holding said second keeper in its removalpreventing position.

12. Apparatus as recited in claim 11 in which said first keeper comprises a cam pivoted about a diameter of said shaft, said cam having a tab thereon;

and a spring, positioned substantially coaxially within said shaft and recessed into said shaft in a position to engage said tab when said cam is rotated into its gearholding position.

13. Apparatus as recited in claim 12 in which said second leg has a clevis formed on the upper end thereof straddling said frame, and said shaft is common to said second leg, said frame, and said gear.

14. Apparatus as recited in claim 13 in which said second leg is articulated and has a scribing instrument positioned on the distal end thereof, including chuck means for holding said scribing instrument.

It! l' i i Patent No. 3,797,119 Dated March 19, 1-974 Ronald N. McDow Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 5 should appear as shown below:

5. In combination:

a drawing compass having two-legs pivoted about a Q pivotal axis one of which supports a worm Whose axis is substantially parallel to a second axis along the length of its supporting leg and which is attached for non-rotation about said second axis; and g l a worm gear, fixedly attached to the other said leg for rotation about said pi votal axis of said compass and meshing with said norm to cause the radius of said compass to vary as said compass in swung.

Signed and sealed this 24th day of September 1974.

(SEAL) Attest: MCCOY M. GIB SONJR. c. MARSHALL 'DANN Attesting Officer Commissioner of Patent:

FORM M 4050 (10-69) USCOMM-DC 50376-P69 i it 0.5. GOVERNMENT PRINTING OFFICE 1989 0-366-334, 

1. A compass-like drawing instrument for making spiral-like curves comprising: a base leg, having a major axis defined along the length thereof, including means thereon for fixedly engaging a reference position on a drawing to prevent translation of said base leg relative to said referenced position and to prevent rotation of said base leg about said major axis; a drawing leg, rotatable about said base leg and pivoted about a pivotal axis to vary the radius of the instrument relative to said base leg and said reference position and adapted to hold a drawing tool on the end thereof distal from said pivotal axis; a mechanical worm, positioned on said base leg with its axis substantially parallel with the said major axis of said base leg, including means for preventing said worm from turning about said axis; and a worm gear, rigidly attached to said drawing leg for rotation about said pivotal axis and meshing with said worm.
 2. A drawing instrument as recited in claim 1 in which said worm and worm gear are each removable from said legs.
 3. Apparatus as recited in claim 2 and further comprising keepers for holding said worm and said worm gear onto their respective legs.
 4. Apparatus as recited in claim 3 in which said worm and worm gear form a matched set, said set being interchangeable with other matched sets to vary the functional relation between the spread angle of the legs of the instrument and the angle through which the instrument is swung.
 5. In combination: a drawing compass having two legs pivoted about a pivotal axis, one of which supports a worm whose axis along the length of its supporting leg and which is attached for non-rotation about said second axis; and a worm gear, fixedly attached to the other said leg for rotation about said pivotal axis of said compass and meshing with said worm to cause the radius of said compass to vary as said compass is swung.
 6. Apparatus as recited in claim 5 in which said worm and worm gear form a matching set, and said set is interchangeable with other matching sets having different pitches and directions of spiral of said worm and gear.
 7. Apparatus as recited in claim 6 and further comprising a first Keeper for holding said worm onto said compass and a second keeper for holding said gear onto said compass.
 8. An instrument as recited in claim 7 and further comprising a plurality of paper-engaging pins upon the foot of said leg which supports said worm.
 9. Apparatus as recited in claim 8 and further comprising a marking implement attached to the foot of said gear-carrying leg.
 10. A compass as recited in claim 9 in which said gear-carrying leg has a hinge therein and including a set screw for fixing a position of said hinge.
 11. A drawing instrument of the compass type for producing spiral-like curves comprising: a first leg including a rotatable sleeve and having a plurality of projecting spikes from the foot of said leg; a mechanical worm having a shank thereon shaped to fit into said sleeve along an axis defined in said first leg including attaching means positioned and adapted to attach said shank and said foot to allow turning of said sleeve relative to said shank about said axis; a frame, attached to said sleeve for rotation about the axis of said worm; a second leg pivotally attached to said first leg for rotation about a second axis, relative to said frame, substantially perpendicular to the axis of said worm and said shank; a spline on said second leg; a segmented worm gear having a groove adapted to mate with said spline in the non-tooth portion of said gear to prevent relative rotation between said gear and said second leg; a shaft on said second leg substantially coaxial with said second axis; said gear being positioned on said shaft and said spline to cause said second leg to turn with said gear; a first keeper on the end of said shaft, positioned and adapted to hold said gear on said shaft, including a spring detent for holding said keeper in its gear-holding position; a second keeper having a blocking plate, pivotally attached to said frame to have at least two positions, one of which prevents the removal of said worm and the other of which allows removal of said worm and including means for holding said second keeper in its removal-preventing position.
 12. Apparatus as recited in claim 11 in which said first keeper comprises a cam pivoted about a diameter of said shaft, said cam having a tab thereon; and a spring, positioned substantially coaxially within said shaft and recessed into said shaft in a position to engage said tab when said cam is rotated into its gear-holding position.
 13. Apparatus as recited in claim 12 in which said second leg has a clevis formed on the upper end thereof straddling said frame, and said shaft is common to said second leg, said frame, and said gear.
 14. Apparatus as recited in claim 13 in which said second leg is articulated and has a scribing instrument positioned on the distal end thereof, including chuck means for holding said scribing instrument. 